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Flashcards in Endodontics Deck (44)
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1

What are the three design objectives of root canal preparation?

Create a continuously tapering funnel shape
Maintain apical foramen in original position
Keep apical opening as small as possible

2

What is the access shape for upper central and lateral incisors?

Triangular, with the point towards the gingival margin

3

What is the access shape for upper canines?

Oval

4

What size of taper do all ISO stainless steel K files have?

02 taper or 2% taper

5

What are the different lengths of ISO instrument files?

21, 25 or 31mm

6

The handles of ISO instruments are colour coded. Which colours represent which file sizes?

Pink - 06
Grey - 08
Purple - 10
White - 15,45
Yellow - 20,50
Red - 25,55
Blue - 30,60
Green - 35,70
Black - 40,80

7

What is the length of the cutting flutes on ISO instruments?

16mm

8

What are the drawbacks of conventional stainless steel preparation techniques?

mishaps (ledges, canal blockage, zipping of foramen)
debris extrusion with filing motion
time consuming
less predictable shapes in curved canals

9

Nickel-Titanium alloy allows files to have superelasticity. What is this and what are it's benefits?

Superelasticity means alloy can be strained more than other alloys before permanent deformation occurs.
It allows NiTi files to be placed in curved canals with less lateral forces exerted - less transportation, zipping or ledging; more centrally placed preparation in harmony with the original canal shape

10

What are the advantages of NiTi vs SS?

-increased flexibility in larger sizes and tapers
-increased cutting efficiency
-better safety in use
-better user friendliness with less instruments and simple sequences

11

What are the disadvantages of NiTi preparation?

-instrument fracture
-expense
-access can be difficult in posterior teeth
-unsuitable for complex canal anatomy

12

ProTaper hand files come in sizes Sx, S1-S2 and F1-F4. What are the tip sizes of the Sx, S1 and S2 files?

Sx = 19
S1 = 17
S2 = 20

13

How is working length calculated?

Working length is measured from a fixed reference point (which will remain unchanged throughout the treatment + is within clinicians field of view)
Determined after coronal flaring
WL should be as close as possible to CDJ - usually the apical constriction (narrowest part of canal)
Can be determined radiographically or by using an electronic apex locator

14

What is a glide path and how do you create one?

Glide path - space created within root canal where instruments can glide in relatively easy and bind/gauge apically
-confirm straight line access, explore anatomy
-introduce files 10-25 to resistance only (coronal only), coronal flare - S1
-size 10 WW (watch winding) establish apex
-irrigate + repeat using size 15 (WW) and size 20 (BF)

15

What is recapitulation and patency filing?

patency filing - use a small file eg size 08/10 through the apical constriction to minimise blockage

16

What is apical gauging?

-decide which file to finish with apically by going 2 file sizes bigger than the first file to bind
-check F files for debris apically when removing - if no debris then file is not engaging
-use K file to check apical binding as K file will not bind coronally or middle 1/3 since taper in canal is larger

17

When obturating, GP points are coated with resin sealers. What are these and what are their properties?

-epoxy resin, two paste mixing system
-slow setting (8 hours)
-good sealing ability
-good flow
-initial toxicity declining after 24 hours
-water resistant (insoluble)

18

What are the contents of GP points?

-gutta percha 20%
-zinc oxide 65%
-radiopacifiers 10%
-plasticisers 5%

19

Describe the cold lateral compaction technique used for obturation.

-Master GP point fits apical collar, tweezers locked at WL
-Master GP point forced to side of canal
-Finger spreader inserted to 2mm from apical stop
-Accessory points used in space created by finger spreader and added until canal is fully obturated
-excess removal of GP done using heated instrument, aim to cut just below ACJ
-use CaOH as a sealer and restore cavity with appropriate material

20

What are the signs and symptoms of reversible pulpitis?

-discomfort is experienced only lasting a few seconds when a stimulus is applied
-exposed dentine (dentinal sensitivity), caries or deep restorations
-no significant radiographic changes in periapical region
-pain experienced is not spontaneous

21

What are the signs and symptoms of irreversible pulpitis?

-may include sharp pain upon thermal stimulus, lingering pain (often 30secs or longer after stimulus removed), spontaneity (unprovoked pain), referred pain
-pain may be accentuated by postural changes such as lying down or bending over
-OTC analgesics typically ineffective
-deep caries, extensive restorations, fractures exposing pulpal tissues
-hyperaemic pulp

22

What are the signs and symptoms of pulp necrosis?

-non-responsive to pulp testing, asymptomatic
-pain to percussion or radiographic evidence of osseous breakdown unless canal is infected

23

What part of sodium hypochlorite is responsible for antibacterial activity?

-NaOCl ionises in water into Na+ and hypochlorite OCl-
-establishes equilibrium with hypochlorous acid (HOCl)
-HOCl is responsible for antibacterial activity

24

What are the properties of sodium hypochlorite?

-potent antimicrobial activity
-dissolves pulp remnants and collagen
-only irrigant that dissolves necrotic and vital tissue
-helps disrupt smear layer by acting on organic component
-time essential for effectiveness: should irrigate for 10mins from when you have accessed the root apex with file

25

What is an endodontic smear layer? How is removal of smear layer achieved?

-organic pulpal material + inorganic dentinal debris, superficial 1-5um layer with packing into tubules
-removed using 17% EDTA (chelating agent), or citric acid
-1min contact time necessary with EDTA

26

What is a general rule of thumb for single visits or multi-visits regarding root canal treatments?

-vital and asymptomatic -> single visit
-all others -> multi-visit
-must be decided on case by case basis

27

K files have are made from a ________ shape therefore have __ points of contact.

Square, 4

28

What are the objectives of root canal objectives?

-to disinfect root canal
-dissolve organic debris
-flush out debris
-lubricate root canal instruments
-remove endodontic smear layer

29

Root canal irrigants are delivered through which type of needle?

-Luer lock syringe
-27 gauge endodontic-tipped needle

30

What are the objectives of cleaning and shaping the root canals?

-remove infected soft and hard tissue
-give disinfecting irrigants access to apical canal space
-create space for the delivery of medicaments and subsequent obturation
-retain the integrity of radicular structures

31

What are the reasons for endodontic failure?

before: misdiagnosis, treatment planning/case selection problems
during: missed canals, ineffective clean, shape or fill; iatrogenic damage
after: recurrent caries; coronal leakage; post hole preparation problems

32

How would you clinically assess a RCT tooth?

Check for:
-coronal seal
-swelling
-sinus
-TTP
-buccal sulcus tender to palpation?
-mobility
-increased pocketing

33

How would you radiographically assess a RCT tooth?

Check for:
-root filling (length, quality of obturation)
-unfilled/missed root canals
-sclerosis
-bone support
-crown to root ratio 1:1.5
-radiolucency

34

What problems are associated after RCT/re-RCT?

-amount of remaining tooth structure
-lack of ferrule
-wide post holes (eg re-RCT)
-endodontic complications eg fractured instruments

35

Are pulp less teeth more brittle than vital teeth?

Reduced structural integrity leads to weakening of tooth, NOT brittleness

36

What is the purpose of a post/core?

To gain intraradicular support for a definitive restoration
Core provides retention for crown
Post retains core

37

What are the guidelines for the width and length of a post?

No more than 1/3 of root width at narrowest point and 1mm of remaining circumferential coronal dentine
Minimum 1:1 post length/crown length ratio

38

What are the guidelines for post placement regarding alveolar bone and ferrule?

Sufficient alveolar bone support must be present - at least half of post length into the root
At least 1.5mm of height and width of remaining coronal dentine

39

What properties does the ideal post have?

Parallel sided
Non-threaded (passive)
Cement retained

40

What is the adv of a parallel sided post than a tapered post?

Avoids wedging
More retentive

41

What are the adv/disadv of a non-threaded cement retained post than a threaded post?

Incorporate less stress to remaining tooth tissue than threaded (active)
Cement acts as buffer between tooth and post during masticatory forces
Less retentive

42

What materials can be used for a core?

Composite - most common
Amalgam
GI

43

What problems are associated with posts?

Perforation, core fracture, root fracture or crack, post fracture.

44

What methods can be used for post removal?

Ultra sonics
Masseran kit
Eggler
Moskito forceps (screw retained)